Valvetrain oil control system and oil control valve

ABSTRACT

A hydraulic control system includes an oil control valve to control oil flow within a valvetrain. The control valve varies the flow rate to actuate an engine component from a first position to a second position based upon fluid pressure from the control valve. Varying the flow rate through the control valve includes increasing the flow rate through the control valve to increase the pressure to a first level to actuate the engine component to the first position. After the engine component is actuated, the flow rate through the control valve is maintained at a level sufficient to maintain the engine component in the first position. To actuate the engine component to the second position the flow rate through the control valve is then decreased. The fluid flow rate through the control valve is then maintained at a level sufficient to maintain the engine component in the second position.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application61/082,575, filed Jul. 22, 2008, which is hereby incorporated byreference in its entirety.

TECHNICAL FIELD

The present invention relates to an oil control system for a valvetrain,and more specifically, to an arrangement and method for reducing oilconsumption by the valve train.

BACKGROUND OF THE INVENTION

A hydraulic control system for an engine supplies oil to various enginecomponents and may also include oil control valves to control oil underpressure that may be used to, for example, switch latch pins inswitching lifters, switching rocker arms, and switching lash adjustersin engine valve train systems. Valve actuation systems include, but arenot limited to, valve deactivation and variable valve lift systems.

Valve lifters are engine components that transfer cam motion whichcontrols the opening and closing of exhaust and intake valves in anengine. Lash adjusters and rocker arms may also be used to change liftprofiles on exhaust and intake valves in an engine. In addition tovarying valve lift, variable valve actuation systems may selectivelyactivate or deactivate the engine valve. The engine valves aredeactivated or locked out to disable operation of some cylinders in anengine when power demands on an engine are reduced. By deactivatingcylinders, fuel efficiency of an engine may be improved.

Engine oil control valves must operate with minimum response times tomaximize engine efficiency and increase engine durability. Latch pinswitching response times include latch pin activation response times anddeactivation response times. In variable valve actuation systems, thelimited time window for valve actuation is critical and must beminimized. Additionally, as the flow rate and pressures within thesystem changes due to temperature and engine speed to actuate thevalves, the oil flow rate to all the system components is similarlyaffected.

SUMMARY OF THE INVENTION

A hydraulic control system is provided for reducing oil consumption ofan engine valve-train. The hydraulic control system includes an oilreservoir and an oil pump fluidly connected to the oil reservoir to pumpoil from the reservoir to at least one engine component.

An oil control valve is fluidly connected to the oil reservoir and theoil pump includes a housing defining a first chamber, a second chamberand a third chamber. A wall of the housing is located between the firstand the second chamber. The wall defines an orifice having an anglededge to form a valve seat. A diaphragm is mounted to the housing andforms a wall between the second chamber and the third chamber. A poppetis mounted on the diaphragm. The poppet extends through the orifice andis moveable relative to the valve seat based upon a change in pressureswithin the first chamber, the second chamber, and the third chamber.Additionally, a solenoid valve selectively fluidly connects the firstchamber to the third chamber.

A method of controlling oil flow within a valve train includes pumpingfluid from a fluid reservoir to a control valve and varying the flowrate through the control valve such that fluid enters the control valveat a first pressure and flows from the control valve at a secondpressure. The fluid from the control valve is directed to at least oneengine component of the valvetrain. The engine component is fluidlyactuated from a first position to a second position based upon thesecond pressure from the control valve.

Varying the flow rate through the control valve includes increasing theflow rate through the control valve to increase the second pressure to afirst level which actuates the engine component to the first position.After the engine component is actuated, the flow rate through thecontrol valve is maintained such that the second pressure is at a secondlevel which is less than the first level and sufficient to maintain theengine component in the first position. To actuate the engine componentto the second position, the flow rate through the control valve is thendecreased to decrease the second pressure to a third level. The fluidflow rate through the control valve is then maintained such that thesecond pressure is at a fourth level that is less than the second leveland sufficient to maintain the at least one engine component in thesecond position.

The above features and advantages and other features and advantages ofthe present invention are readily apparent from the following detaileddescription of the best modes for carrying out the invention when takenin connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of a hydraulic control system;

FIG. 2 is plot of pressure within the supply and control galleriesversus time for the hydraulic control system in FIG. 1;

FIG. 3 is a schematic cross-sectional illustration of a variable flowvalve for use with the hydraulic control system of FIGS. 1 and 2.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1, wherein like reference numbers refer to the same orsimilar components throughout the several views, a hydraulic controlsystem 10 is illustrated. The hydraulic control system 10 includes anoil reservoir 12 and an oil pump 14. The oil pump 14 pumps oil from theoil reservoir 12 to various engine components 16. The engine components16 includes at least one engine component 16A which includes a latch pin18 for actuation of the at least one engine component 16A between anengaged and disengaged position. The at least one engine component 16Acould be a lash adjuster, a valve lifter, or a rocker arm. Although theembodiment described below is with reference to one latch pin 18,multiple latch pins 18 may be actuated at one time. The enginecomponents 16 also include other valve-train components such asbearings.

Engagement and disengagement of the latch pin 18 within the at least oneengine component 16A is actuated by the hydraulic control system 10 asdescribed below. For example, the at least one engine component 16A is alash adjuster that changes the lift properties for engine intake andexhaust valves, as is known by those skilled in the art. Oil from theoil pump 14 passes through a oil control valve assembly 20 to the enginecomponents 16 including the at least one engine component 16A beforereturning to the oil reservoir 12.

The oil control valve assembly 20 includes a solenoid valve 22 and avariable flow valve 24. The oil control valve assembly 20 varies theflow rate from an oil supply gallery 26 to a control gallery 28 to varypressure within the control gallery 28. The variation in pressure withinthe control gallery 28 will engage or disengage the latch pin 18. Oilflow from the control gallery 28 also flows to the other enginecomponents 16 prior to returning to the oil reservoir 12.

Referring to FIGS. 1 and 2, a method of operating the oil control system10 is explained in further detail. Oil enters the variable flow valve 24from the supply gallery 26 at a first pressure P₁. Oil flow is directedthrough the variable flow valve 24 to the control gallery 28 which is ata second pressure P₂. The second pressure P₂ of the control gallery 28is a sufficient pressure to lubricate the engine components 16. Anexemplary maintenance pressure for lubricating and assuring performanceof the engine components 16 is 5-12 psi within the control gallery 28.As oil enters the engine components 16 at the P₂, the variable flowvalve 24 increases or decreases flow in an effort to reach pressurebalanced equilibrium within the variable flow valve 24.

The solenoid valve 22 includes an electromagnetic coil 23. When theelectromagnetic coil 23 for the solenoid valve 22 is energized, a bypass30 to the solenoid valve 22 is opened. Oil from the supply gallery 26flows through the solenoid valve 22 to a chamber 32 within the variableflow valve 24. The increased pressure within the chamber 32significantly biases the pressure balanced equilibrium within thevariable flow valve 24 and adjusts the variable flow valve 24 toincrease the flow rate from the supply gallery 26, to the controlgallery 28. The sudden increase in flow rate into the control gallery 28causes pressure within the control gallery 28 to increase, which resultsin sufficient pressure to effect actuation of the latch pin 18.Actuation of the latch pin 18 moves the latch pin 18 from a firstposition to a second position. In the embodiment shown the latch pin 18is a normally engaged pin and actuation of the latch pin 18 from thefirst position to the second position moves the pin from an engagedposition to a disengaged position. An example of the latch pin 18disengagement pressure P_(DIS) for the embodiment shown is 15-20 psi.This is illustrated by the dashed lines of FIG. 2. Due to the suddenincrease in flow rate into the control gallery 28 from the supplygallery 26, the control gallery 28 pressure P₂ will increase to a firstlevel well past the latch pin 18 disengagement pressure P_(DIS). Therate of the pressure increase within the control gallery 28 isillustrated by the slope of P₂ on FIG. 2. The over-rise in pressuredecreases the time taken for the control gallery 28 to increase to thedisengagement pressure P_(DIS). That is, the rate of pressure increase(the slope of P2) is steeper, reaching the disengagement pressureP_(DIS) sooner and actuating the latch pin 18 more quickly. Thus, thetravel time to actuate the latch pin 18 is decreased.

Once the latch pin 18 is disengaged, the increased flow rate from thesupply gallery 26 to the control gallery 28 that maintains the higherpressure P₂ in the control gallery 28 is not necessary. This higherpressure increases the oil flow through the engine components 16 andback to the reservoir 12, which decreases the engine efficiency.However, the pressure P2 in the control gallery 28 must be maintainedabove an engagement pressure P_(DIS) for the latch pin 18 such that thenormally engaged latch pin 18 is maintained in the second position,which in this embodiment is the disengaged position. As the pressure P₂in the control gallery 28 increases, the variable flow valve 24re-establishes an equilibrium force between the spring 58 at a reducedload, the pressure in chamber 32 against the diaphragm 52, and thepressure in chamber 24 against the diaphragm 52. Pressure also acts onthe poppet 50 from the first chamber 42 and the second chamber 44. Theflow rate from the supply gallery 26 to the control gallery 28 settleswith the control gallery pressure P₂ at a second level. The flow rate isgreater than the flow rate when the solenoid valve 22 is off and thebypass 30 is closed. However, the variable flow valve 24 also allows theflow rate to settle such that the pressure P₂ in the control gallery 28at the second level is only slightly above the pressure required tomaintain the latch pin 18 in the second position. In the embodimentshown, the control gallery 28 is at a pressure of approximately 30 psiand the pressure to maintain the second position for the latch pin 18 isat 25 psi. The flow rate creating this pressure can be maintained untilit is time to move the pin 18 back to the first position, which is theengaged position in this embodiment. The variable flow valve 24 allowsthe flow rate to the control gallery 28 to settle at a lower flow rate,resulting in the lower pressure in the control gallery 28. Therefore,the oil flow through all the engine components 16 is reduced, reducingoil consumption of the engine components 16 after the latch pin 18 hasbeen moved to the second position and prior to the latch pin 18 beingmoved back to the first position.

When it is time to reengage the latch pin 18, the magnetic coil 23 forthe solenoid valve 22 is de-energized. The solenoid valve 22 switches toan exhaust position. The bypass 30 from the supply gallery 26 to thechamber 32 is closed. However, the chamber 32 is now opened through thesolenoid valve 22 to the exhaust gallery 34. Oil within the chamber 32drains back to the oil reservoir 12. The sudden pressure loss within thechamber 32 causes the force balance within the variable valve 24 to biasthe poppet 50 toward the valve seat 46 shutting off the flow to secondchamber 44 and control gallery 28. Thus, the pressure within the controlgallery 28 drops to a third level. Similar to when the latch pin 18 isdisengaged, the pressure change in the in the control gallery 28 is morethan what is needed to move the latch pin 18. Thus, the actuation timeto re-engage the latch pin 18 is decreased. Additionally, because thevariable flow valve 24 previously allowed the pressure P₂ within thecontrol gallery 28 to remain only slightly above the disengagementpressure P_(DIS) of the pin 18, the engagement pressure P_(ENG) of thelatch pin 18 is reached quickly which also reduces the actuation time.

Once the latch pin 18 is engaged, the variable flow valve 24re-establishes an equilibrium force between the spring 58 at anincreased load, the lower pressure in the third chamber 32 acts againstthe diaphragm 52, and the pressure P₂ in the second chamber 44 also actsagainst the diaphragm 52. Pressure is also acting on the poppet 50 fromthe first chamber 42 and the second chamber 44. The flow rate settles ata fourth level that maintains pressure sufficient to maintain engineperformance and lubricate the engine components 16. As mentioned above,in the embodiment illustrated in FIG. 2, the flow rate is such that thepressure P₂ within the control gallery 28 is approximately 10 psi.

Although the above embodiment is described as having at least one enginecomponent 16A with a normally engaged latch pin 18 that may bedisengaged with the oil control valve 20, the at least one enginecomponent 16A may alternately be a normally disengaged pin 18 which isengaged with the oil control valve 20. One skilled in the art would knowthe proper arrangement for the at least one engine component 16A andlatch pin 18 based upon the engine and oil control system 10 for whichit is used.

Referring to FIG. 3, an embodiment of a variable flow valve 24 isillustrated. The variable flow valve includes a housing 40 defining afirst chamber 42 and a second chamber 44. An orifice 46 is defined by awall 48 which divides the first chamber 42 from the second chamber 44.Oil enters the first chamber 42 from the supply gallery 26 at a firstpressure P₁ and flows through the orifice to the second chamber 44 whichis at the second pressure P₂ and connected to the control gallery 28. Inthe embodiment shown, the orifice 46 has an angled edge defined by thewall 48 which acts as a seat for a poppet 50. Other arrangements for theorifice 46 to form a valve seat may also be utilized, such as the wall48, may be flat or otherwise shaped to form the valve seat. One skilledin the art would know the proper arrangement for a valve seat given thevariable flow valve 24 application and specifications.

The poppet 50 is mounted to a diaphragm 52. The diaphragm 52 is locatedbetween the second chamber 44 and a third chamber 32. The diaphragm 52seals the second chamber 44 from the third chamber 32 and allows thepoppet 50 to move along an axis A. A damper 56 is located at an opposingend of the poppet 50 and dampens oscillations of the poppet 50 thatwould occur as a result of the changes in the pressure between the firstchamber 42, the second chamber 44 and the third chamber 32. In theembodiment shown the damper 56 is illustrated as a fluid damper 56.However, other types of dampers may be utilized as is known to thoseskilled in the art. A spring 58 is located in the third chamber 32 andbiases the poppet 50 to a neutral open position as shown in FIG. 3. Thespring 58 acts upon a support 60 which is secured to and protects thediaphragm 52.

As described above, and with reference to FIGS. 1 and 2, fluid from thesupply gallery 26 enters the first chamber 42 and flows through theorifice 46 into the second chamber 44, where it then exits the flowcontrol valve 24 to the control gallery 28. When the electromagneticcoil 23 for the solenoid valve 22 is energized the bypass 30 is openedand fluid also flows from the supply gallery 26, through the firstchamber 42, into the bypass 30 and through the solenoid valve 22 to thethird chamber 32. The pressure within the third chamber 32 increases andthe resulting pressure differential between the second chamber 44 andthe third chamber 32 results in unbalancing the force balance equationand creating a biasing force at the diaphragm 52. Therefore, oil flowinginto the third chamber 32 forces the diaphragm to flex and moves thepoppet 50 axially along the axis A to open the orifice 46 to a greaterextent and increase the flow rate from the first chamber 42 to thesecond chamber 44. Thus, flow from the supply gallery 26 to the controlgallery 28 is increased when the solenoid valve 22 is activated.Additionally, because the orifice 46 is larger in diameter than thevalve seat (not shown) within the solenoid valve 22 a smaller magneticcoil 23 is sufficient to energize the solenoid valve 22. Thus, reducingthe amount of copper required by the magnetic coil 23, the current tothe solenoid valve 22, and the amount of oil pressure required to openthe solenoid valve 22. Because the size of the orifice 46 allows forincreased flow rate of fluid to the control gallery 28 this alsoincreases the rate of latch pin 18 motion and increases the pressurerise (the slope of P₂) from P_(DIS) to P_(ENG 0)on the oil controlsystem 10 over systems having smaller flow rates to the control gallery28.

After the initial flow of fluid into the third chamber 32, the forceapplied to the diagram 52 will balance. The variable valve 24 willstabilize at a point that allows increased flow from the first chamber42 to the second chamber 44 than when the solenoid valve 22 is notenergized. The pressure increase in the point of equilibrium is based onthe force balance equation. The force balance equation is the force ofspring 58 plus the force on the area of the diaphragm 52 multiplied bythe pressure within the third chamber 32 minus the force due to the areaof the orifice 46 times the control gallery 28 pressure P₂, which isequal to the force due to the area of the orifice 46 times the supplygallery 26 pressure P₁ plus force on the area of the diaphragm 52 timesthe control gallery 28 pressure P₂. This is represented by the followingforce balance equation:

F(spring 58)+F((area of diaphragm 52)*P(chamber 32))−F((area of orifice46)*P ₂)=F((area of orifice 46)*P ₁)+F((area of diaphragm 52)*P ₂)

When the solenoid valve is de-energized, the bypass 30 is fluidlydisconnected from the third chamber 32. The fluid within the thirdchamber 32 exits through the exhaust gallery 34 (shown in FIG. 1) to theoil reservoir 12. The flow of oil out of the third chamber 32 decreasesthe pressure within the third chamber 32 and the fluid pressure P₂within the second chamber 44 to cause the poppet 50 to move axiallyalong the axis A to reduce flow through orifice 46. Due to the extremedelta pressures on both sides of the diaphragm 52 and unbalancing of theforce balance equation, the poppet will momentarily close the orifice46. As the pressure P2 in the second chamber 44 drops, the poppet beginsto reopen until the force balance equation come back to equilibrium. Thespring 58 prevents the fluid pressure P₁ in the first chamber 42 fromkeeping the orifice 46 closed. Fluid continues to flow from the firstchamber 42 to the second chamber 44, although at a reduced rate thanbefore. The poppet 50 is again in the position shown in FIG. 3 whichallows fluid to flow into the control gallery 28 at a sufficient rate tomaintain the minimal pressure P₂ needed to lubricate the enginecomponents 16.

While the best modes for carrying out the invention have been describedin detail, those familiar with the art to which this invention relateswill recognize various alternative designs and embodiments forpracticing the invention within the scope of the appended claims.

1. A hydraulic control system for a valve train comprising: an oilreservoir; an oil pump fluidly connected to the oil reservoir; at leastone engine component in fluid communication with the oil pump and theoil reservoir; an oil control valve in fluid communication with the oilreservoir and the oil pump; wherein the oil enters the oil control valveprior to the at least one engine component; and wherein the oil controlvalve includes: a housing defining a first chamber, a second chamber anda third chamber; a wall of the housing located between the first and thesecond chamber; wherein the wall defines an orifice to form a valveseat; a diaphragm mounted to the housing and forming a second wallbetween the second chamber and the third chamber; a valve member mountedon the diaphragm, wherein the valve member extends through the orificeand is moveable relative to the valve seat based upon a change in fluidpressures within at least one of the first chamber, the second chamber,and the third chamber; and a solenoid valve to selectively fluidlyconnect the first chamber to the third chamber.
 2. The hydraulic controlsystem of claim 1, wherein the valve member is in a first positionrelative to the valve seat when the solenoid valve fluidly connects thefirst chamber to the third chamber and in a second position relative tothe valve seat when the solenoid valve fluidly disconnects the firstchamber from the third chamber.
 3. The hydraulic control system of claim2, wherein the solenoid valve fluidly connects the third chamber to thefluid reservoir when the first chamber is fluidly disconnected from thethird chamber.
 4. The hydraulic control system of claim 2, wherein thefluid within the first chamber is at a first pressure and fluid withinthe second chamber is at a second pressure; wherein the second pressureis lower that the first pressure; and wherein the pressure differentialbetween the first chamber and the second chamber biases the valve memberin a first direction toward the valve seat.
 5. The hydraulic controlsystem of claim 4, wherein the oil control valve further comprises aspring located within the third chamber to bias the valve member in asecond direction away from the valve seat.
 6. The hydraulic controlsystem of claim 4, wherein the second pressure is at a first level whenthe solenoid valve fluidly connects the first chamber to the thirdchamber and at a second level, lower than the first level, when thesolenoid valve fluidly disconnects the first chamber from the thirdchamber.
 7. An oil control valve comprising: a housing defining a firstchamber, a second chamber and a third chamber; a wall of the housinglocated between the first and the second chamber, wherein the walldefines an orifice; a diaphragm mounted to the housing and forming awall between the second chamber and the third chamber; a valve membermounted on the diaphragm, wherein the valve member extends through theorifice and is moveable relative to the orifice based upon a change inpressures within at least one of the first chamber, the second chamber,and the third chamber; and a solenoid valve fluidly connected to thefirst chamber and the third chamber.
 8. The oil control valve of claim7, wherein the wall defines an angled edge at the orifice, and whereinthe angled edge forms a valve seat for the valve member.
 9. The oilcontrol valve of claim 8, wherein the valve member is in a firstposition relative to the valve seat when the solenoid valve fluidlyconnects the first chamber to the third chamber and in a second positionrelative to the valve seat when the solenoid valve fluidly disconnectsthe first chamber from the third chamber.
 10. The oil control valve ofclaim 8, wherein fluid within the first chamber is at a first pressureand fluid within the second chamber is at a second pressure, wherein thesecond pressure is lower that the first pressure and the pressuredifferential between the first chamber and the second chamber biases thevalve member in a first direction toward the valve seat.
 11. The oilcontrol valve of claim 10, wherein the oil control valve furthercomprises a spring located within the third chamber to bias the valvemember in a second direction away from the valve seat.
 12. The oilcontrol valve of claim 10, wherein the second pressure is at a firstlevel when the solenoid valve fluidly connects the first chamber to thethird chamber and at a second level, lower than the first level, whenthe solenoid valve fluidly disconnects the first chamber from the thirdchamber.
 13. The oil control valve of claim 7, wherein the solenoidvalve fluidly connects the third chamber to an exhaust gallery when thefirst chamber is fluidly disconnected from the third chamber.
 14. Theoil control valve of claim 7, wherein the valve member is connected tothe housing with a damper.
 15. A method of controlling oil flow within avalve train comprising: pumping fluid from a fluid reservoir to acontrol valve; varying the flow rate through the control valve such thatfluid enters the control valve at a first pressure and flows from thecontrol valve at a second pressure; directing fluid from the controlvalve to at least one engine component of the valve train, wherein theat least one engine component is fluidly actuated from a first positionto a second position based upon the second pressure; and wherein varyingthe flow rate through the control valve includes; increasing the flowrate through the control valve to increase the second pressure to afirst level to actuate the at least one engine component to the firstposition; maintaining the flow rate through the control valve such thatthe second pressure is at a second level which is less than the firstlevel and sufficient to maintain the at least one engine component inthe first position; decreasing the flow rate through the control valveto decrease the second pressure to a third level to actuate the at leastone engine component to the second position; and maintaining the flowrate through the control valve such that the second pressure is at afourth level which is less than the second level but greater than thefourth level and sufficient to maintain the at least one enginecomponent in the second position.
 16. The method of claim 15, whereinvarying the flow rate through the control valve further includesdirecting fluid within the control valve from a first chamber at thefirst pressure to a second chamber at the second pressure by moving avalve member relative to a valve seat located between the first and thesecond chamber.
 17. The method of claim 16, wherein varying the flowrate through the control valve further includes activating a solenoidvalve to fluidly connect the first chamber to a third chamber to movethe valve member in a first direction away from the valve seat toincrease the second pressure to the first level and then maintain thesecond pressure at the second level.
 18. The method of claim 17, whereinvarying the flow rate through the control valve further includesdeactivating a solenoid valve to fluidly disconnect the first chamberfrom the third chamber to move the valve member in a second directiontoward the valve seat to decrease the second pressure to the third leveland then maintain the second pressure at the fourth level.
 19. Themethod of claim 16, further comprising damping vibrations of the valvemember resulting from the changes in pressure between the first chamberand the second chamber.
 20. The method of claim 15, wherein maintainingthe flow rate through the control valve such that the second pressure isat a second level to maintain the at least one engine component in thefirst position further includes maintaining a normally engaged lashactuator in a disengaged position; and wherein maintaining the flow ratethrough the control valve such that the second pressure is at a fourthlevel to maintain the at least one engine component in the secondposition further comprises maintaining the normally engaged lashactuator in an engaged position.